Process for producing potentially adhesive textile fibers



.Patented June 26, 1945 UNITED STATES- PATENT OFFICE PROCESS FOR PRODUCING ro'rEN'rmax ADHESIVE TEXTILE FIBERS Roger Wallach, Briarclifl Manor, N. Y., asslgnor,

by mesne assignments, to American Viscose Corporation, Wilmington, Del., a corporation of Delaware 2 Claims.

The invention relates in general to a process for the production of textile fibers, to the fibers so produced, and includes correlated improvements designed to enhance the quality, structure and properties of such fibers whereby to extend their use in the textile and cordage arts.

It has been proposed heretofore to produce alkali-soluble cellulose ethers from fibrous cellulose by treating the cellulose with a suitable etherifying agent in the presence of an alkali. Such prior processes have always been carried out on cellulose fibers of less than textile making length such, for example, as sulphite cellulose, wood pulp, cotton llnters and the like. Further, it has been customary heretofore to grind the cellulose fibers during treatment with alkali and/or etherifying agent to increase the rate of reaction and to produce a uniform product. Such grinding breaks the fibers so that even if the prior practice had employed raw materials comprising fibers of textile-making length, the final product would, in any case, be unsuited for use in the textile and cordage arts. However, the fibers in the products produced by such prior processes were not capable of being separated by carding and combing because the conditions of alkalization, etherifying and purification were not properly controlled to produce a dried product in which the individual fibers could be separated by carding, combing and the like. In most cases, the concentration of the alkali and the temperature of reaction was such that the fibrous form of the cellulose was completely destroyed because the alkali either dissolved the fibres or gelatinized them to such an extent that they would stick together, since it was the object of such prior processes to produce a homogeneous product which could be readily dissolved.

In contrast to the prior practice in making cellulose ethers, the present invention utilises as raw material a mass of loose cellulose fibers of textile-making length and avoids any shredding or breaking of the fiber before, during or after etherification, andfurther provides that the etherification and purification are carried out under such conditions that the fibrous form of the raw material is preserved to such an extent that the individual fibers in the dried product can be readily separated by carding, combing and the like.

It is a n ral je t of the invention to produce a cellulose ether in the form of separable fibers of textile-making length and which are suitable for use in the textile and cordage arts.

It is a more specific object of the invention to fibers of textile-making length and which are solfibers below atextile-making length and the produce a cellulose ether in the form of'separable uble more or less completely in alkali and insoluble in water.

It is another specific object of the'invention to produce an alkali-soluble cellulose ether in the form or separable fibers of textile-making length while preventing a substantial degradation of the cellulose molecules with a resulting weakening of the fibers of the product.

According to this invention, a substantial curl, that is a wool-like character, is produced or enhanced by converting cellulose of the fibers into an alkali-soluble cellulose ether while maintaining or substantially maintaining the macroscopic form of the fibers.

Thus the product of the present invention is characterized by having the macroscopic fibrous form of the raw fibrous material from which it was prepared and having a textile-making length, but having a substantial curl, which imparts to the fibers a wool-like character. Accordingly, the product of the present invention is adapted for use in many structures of the textile and cordage arts for which the cellulose fibers heretofore known are not adapted, or not as well adapted.

Heretofore'the chemical treatment of cellulose, whether in fibrous form or not, has had for its object the making of a product which may be dissolved in a solvent and then formed into filaments. Thus, it was. customary to start with a raw material which was finely comminuted such as wood pulp, sulphite cellulose or cotton linters, all of which comprise fibers not long enough to be used in the textile and cordagearts. Moreover, to insure a uniform chemical treatment and a uniformly soluble product, it was customary, heretofore, to comminute the cellulose before or during reaction as by shredding. In contrast thereto, in the present invention cellulose is treated in the form of fibers having initially a length capable of being utilized in the textile and cordage arts, .while avoiding any shredding or other comminuting of the fibers before, during or after reaction so as to prevent breaking of the macroscopic form of the fibers is substantially preserved.

Thus the conversion of the cellulose of the fibers is carried out while balancing the determining factors, such as mole relation of the reacting agents, the concentration and nature of the reacting agents and the temperature of the reaction so that the fibers are prevented from sticking together to obtain a product which consistsof wool-like fibers of textile-making length which after drying are capable oi being separated from each other by means of carding, combing and the like. Thus, the temperature maintained may be higher than that at which the alkali present during the reaction causes the fibers to stick together.

Preferably, the conversion is carried out on fibers which are in a swollen condition as a result of treatment with a suitable swelling agent.

Since the conversion treatment usually shrinks the fibers, the wool-like characteristic is enhanced by shrinking the swollen fiber. The swelling of the fiber is carried out under such conditions of temperature and concentration of swelling agent that the fibers are prevented from sticking together.

By the process according to this invention it is thus possible not only to retain the macroscopic fibrous form of the raw material, but also to obtain the product in the form of fibers capable of being separated readily one from another and which have novel wool-like characteristics, all of which make the product of the present invention spinnable and adapted for wider use in the textile and cordage arts.

The invention accordingly comprises the several steps and relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

In the present invention the expression "fiber is intended to include all continuous filaments, whether artificial or naturally occurring, also staple fibers or "chappe obtained by cutting continuous artificial filaments or natural fibers into fibers of textile-making lengths, and all naturally occurring vegetable fibers oi textile-making length.

The expression "cellulose" as used herein is intended to include both cellulose in its naturally occurring state as well as cellulose hydrate an cellulose derivatives of all kinds.

Among the naturally occurring fibers for which the present invention is especially adapted are all those normally smooth-surfaced and/or relatively straight vegetable fibers derived from plants, such as sisal, hemp. jute, fiax, palm, manilla, cocoanut, ramie, China-grass, seaweed, cornstalk, and vegetable hairs, including cotton and kapok, and in general, all plant fibers which have a fiber length sufficient to enable them to be used in the textile or cordage arts.

Artificial cellulose filaments which may be utilized in the invention are cellulose hydrate or regenerated cellulose obtained from viscose or solutions of cellulose in organic or inorganic solvents or cuprammonium cellulose.

The vegetable fibers may be subjected to any suitable treatments for the removal of non-cellulosic constituents which might interfere with the swelling and/or conversion reactions and which might render the fibers incapable of being readily separated by carding, combii g and the like. For example, the resins, pecti l8, lignins, waxes, etc., may be removed from the naturaloccurring cellulose fibers in a known manner, prior to the conversion of such materials. Preferably, with the straight vegetable fibers, such as hemp, jute, flax, etc., the fibers are heated with dilute alkali to remove the non-cellulosic constituents and/or bleached in a known manner before conversion.

It is to be understood that no claim is made to swelling or mercerizing fibers per so when not used in conjunction with a chemical conversion of the cellulose of the fiber as herein described.

For swelling a naturally occurring cellulose fiber or a fiber composed in whole or in part of a cellulose hydrate, the swelling agent may include bases such as sodium hydroxide, potassium hydroxide, tetra-alkyl ammonium hydroxides and organic bases, such as amines; alkaline salts, such as sodium acetate, di-sodium phosphate; acids either inorganic or organic, such as sulphuric, phosphoric, citric, formic, acetic and the like; acid salts, such as ammonium hydrogen sulphate, mono-sodium di-hydrogen phosphate, zinc chloride, also alkali metal thiocyanates, and the like. The swollen fibers of any kind may be carded to loosen them up before they are converted.

By way of illustrating, but not by way of limiting the invention, there may be given the following example of methods of converting naturally-occurring cellulosic vegetable fibers or cellulose hydrate fibers of all kinds:

Methods involving substitution of the hydroxylradical in the cellulose by an organic substituent, for example by converting the cellulose in fiber form completely into a cellulose ether, mixed ether, mixed ester-ether and the like.

For transforming artificial filaments made of cellulose derivatives into fibers having wool-like characteristics, the filaments are treated to convert the cellulose derivative to a cellulose ether. By way of illustrating, but not by way of limiting the invention, such conversion may be accomplished by one or more of the following reactions:

(I) Converting the cellulose derivatives into a cellulose ether having different chemical substituents as by substitution, or

(2) Into a cellulose ether of the same chemical nature but of lower or higher extent of substitution.

- The above methods may be generally classified for convenience as comprising:

(a) The introduction of substituents, or

(b) The-conversion of one type of substituent into another type. I

Thus according to the present invention, a vegetable material in the form of separable fibers is converted to an alkali-soluble cellulose ether in fibrous form by swelling the vegetable fibers with an alkali and the swollen fibers etherified with a suitable etherifying agent in an alkaline medium at a temperature and a concentration of alkali such that the fibers do not stick together and thereafter the alkali is removed and the product obtained in the form of separable fibers.

When converting cellulose to a cellulose ether there may be employed for the alkali an inorganic or organic base such, for example, as sodium hydroxide, potassium hydroxide, di-methyl amine, quaternary ammonium hydroxides, in particular a tetra-benzyi ammonium hydroxide. During the alkalizing treatment, the concentration of the alkali may be from 10% to 25% by weight. During etherification the ratio by weight of dry cellulose on the basis of Cal-1100s to solid alkali calculated as NaOH preferably should not exceed 1 :0.2, the water present during reaction being such that the concentration of the alkali solution is not above 25%, preferably from 10 to 15%.

For the etherifying agent, there may be employed any suitable alkyl ester of an inorganic acid such, for example, as ethyl chloride, diethyl sulphate and the like or a halogen derivative of a polyhydric alcohol such, for example, as ethylene chlorhydrin, epichlorhydrin and the' like, or an alkylene oxide such, for example, as ethylene oxide, propylene oxide; also glycides and the like.

- It is understood that when a halohydrin is employed, sufficient alkali should be present to react therewith so as to split off a hydro-halogen and form the alkylene oxide in situ. The mole ratio of cellulose, calculated as CcHroOs, to the etherifying agent, calculated as ethylene oxide, is not substantially less than 1:0.3. However, an excess of etherifying agent may be employed, if desired, and the excess withdrawn after reaction.

The conditions under which the etherifying reaction takes place should be carefully controlled. In general this reaction should be carried out while the cellulose is in an alkaline medium. The temperature of the etherifying treatment may be varied having regard for the nature of the cellulose and the nature of the particular etherifying agent employed. When cotton is employed as the raw material and ethylene oxide as the etherifying agent, a suitable temperature for reaction is from 15 C. to 30 C. The reaction is preferably carried out in a closed vessel. After removing the unused etherifying agent, as by centrifuging or'by evacuation of the agent, the product is washed and then again centrifuged, and allowed to dry or dried at elevated temperature preferably by blowing a blast of warm air upward through the mass ofwool-like fibers.

When the conversion process is one which tends to give a fibrous product which tends to dissolve, the sticking together of the fibers during treatment and the solubility of the converted cellulose may be prevented or retarded by carrying out the swelling and/or conversion in the presence of a large quantity of a water-soluble inert salt. For example, in converting cellulose to a cellulose ether there may be added to the alkali or to the reaction mixture from to 20% by weight of a salt such as sodium or potassium chloride, sodium or potassium sulphate, sodium or potassium nitrate, and the like.

It is to be understood that, generally, with non-uniform,natural or artificial cellulose fibers the swelling and/or conversion is complete conversion of the cellulose, that is, the conversion may extend throughout the cross-section of the fiber and throughout the length.

It is to be understood that the treatment with the swelling agents and/or with the chemical conversion agents as herein described are carried out on cellulosic fibers which have a length at least sufficient for use in making textiles, that is, the fibers may be continuous filaments or staple fiber of textile-making length, and that any shredding, grinding or breaking of the fibers below a length which would render them unsuitable for use in textiles is avoided.

The treatment of cellulosic fibers according to the invention may be carried out on the fibers per se before, during and/or after their purification or in conjunction with various fiber treatments either manufacturing or finishing, such, for example, as before, during and/or after carding, roving, dyeing, bleaching, sizing, weighting, delustering, mothproofing, waterproofing, fireproofing and the like.

The cellulose fiber may be mixed with an inert fibrous material before being swollen and/or converted to wool-like fibers. For example, one may employ a mixtureof any vegetable fiber and a mineral fiber such as asbestos or glass or a' mixture of a vegetable fiber and synthetic inert fibers, such as resin or rubber.

In the now preferred embodiment, the cellulose fibers to be treated may be cut to suitable staple lengths, if necessary, and after swelling, and pressing the swollen fibers as dry as possible, subsequently carding the fibers before conversion to produce a loose card sliver or a roving sliver, by which the fibers are arranged in substantially arallel relationship. The conversion,

is then carried out preferably continuously on the fibers in the sliver without mechanically disturbing them whereupon there is obtained a fibrous product which can be more readily separated by carding, combing and the like. Thereafter the converted wool-like fibers are purified, dried and fabricated by known means, i. e., carded, spun, woven into textiles.

The new and novel fibers produced by the present invention enables one to obtain new textiles having technically valuable properties which had not been obtained heretofore by the use of known natural or artificial fibers. The effects obtainable in textiles can b varied widely according to the raw fiber treated and to the particular methods of swelling and/or converting to which they are subjected in the present invention. Among other uses, the fibers of the invention may be employed alone or in admixture with each other or with untreated artificial or natural fibers in the fabrication of various types of textiles such, for example, as slivers, rovings, yarns, threads and cords of all kinds, whether single or plied, fabrics of all kinds as made by weaving, knitting, netting, lacing, braiding, and other fabrication processes, and felts of all kinds, including felts for use as fabrics or for use in insulating against pressure, light, sound .or heat, or for use as absorbents for liquids, diaphragms, filters in accordance with the processes described and claimed in the copending U. S. application Serial No. 201,851, filed April 13, 1938, now U. S. Patent No. 2,252,999, issued August 19, 1941.

By the present invention there is obtained a new and novel series of fibers having technically valuable properties which are not found in known natural or artificial fibers. In fact, the wool-like fibers of the invention retain many of the valuable properties of the fibers from which they were produced such as fibrousform, tenacity, and the like and, in addition, acquire the property of complete solubility in aqueous alkali solvents.

This application is a division of my U. S. application Serial No. 232,895, filed October 1, 1938,

. now U. S. Patent No. 2,264,229, issued'November 25, 1941. Since certain changes in carrying out the above process, and certain modifications in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process for producing potentially adhesive textile fibers in a loose separable condition which adapts them to be readily blended with other fibers comprising etherifying cellulosic textile" fibers of staple length while such staple fibers are,

in a loose unspun condition with an etherilying agent in the presence oi! alkali, continuing the etherifying reaction until the staple fibers are converted into cellulose ether staple fibers which are soluble in aqueous alkali solutions but insoluble in water, thereupon discontinuing said etheritying reaction, the temperature during reaction being maintained higher than that at which the alkali present during the reaction will cause the cellulose ether fibers to stick together, washing the cellulose ether staple fibers, drying said washed staple fibers by blowing warm air upwards through the mass of fibers, and carding said dried staple fibers whereby there is produced a mass of cellulose ether staple fibers having the macroscopic form and fiber length of the initial cellulosic staple fibers and having a wool-like appearance, a substantial curl and being in a loose, readily separable condition.

2. A process for producing potentially adhesive textile fibers in a loose separable condition which adapts them to be readily blended with other fibers comprising carding cellulosic textile fibers of staple length with other textile staple fibers which are inert to etherification, ether-flying said mixture of textile staple fibers while the mixture of staple fibers is in a loose unspun condition with an etherifying agent in the presence ot'alkali, continuing the etheriiying reaction until the cellulosic staple fibers in the mixture are converted into cellulose ether staple fibers which are solubl in aqueous alkali solutions but insoluble in water, thereupon discontinuing said etherifying reaction, the temperature during reaction being maintained higher than that at which the alkali present during the reaction will cause the cellulose ether fibers to stick together, washing the mixture containing the cellulose ether staple fibers and drying said washed staple fibers by blowing warm air upwards through the mass oi. fibers, and carding the mixture of dried staple fibers whereby'there is produced a mixture of staple fibers containing cellulose ether staple fibers having the macroscopic form and fiber length of the initial cellulosic staple fibers and having a wool-like appearance, a substantial curl, said mixture of fibers being in a loose readily separable condition.

ROGER WALLACH. 

